It is known that welding electrodes must be sequentially subjected to a lapping operation and that welding robots generally have two electrodes with truncated cone shaped ends which must be lapped on their conical portions and their flat portions.
An apparatus for the purpose described is controlled by the electronic brain of the robot for simultaneously lapping the two electrodes in a first operation so as to lap the conical portions and a second operation for lapping the flat ends. This apparatus comprises means for driving, with a simultaneous reciprocating rotational movement, a spindle having a milling tool for the conical portions and a spindle having a lapping tool for the flat portions, as well as means for centering the spindles with respect to the apparatus.
Because of the acceptable positional tolerance for the head of the robot, this head is subjected to a stress when the electrodes are engaged in the lapping tools. Furthermore, the welding electrodes form an angle with each other which may be large. When they are presented simultaneously for lapping they are not perpendicular to the axis of the milling tool. After a number of milling operations, the contact point between the electrodes and the milling tool moves in space, so that the head of the robot is increasingly stressed.